Rope tensioning device



31, 1956 c. H. ARNOLD ROPE TENSIONING DEVICE 2 Sheets Sheet 1 Filed June 9, 1955 [NVEN TOR. CARTER h. ARNOLD ATTORNEYS y 1, 1956 c. H. ARNOLD ROPE TENSIONING DEVICE 2 Sheets-Shset 2 Filed June 9, 1955 INVENTOR. CARTER h. ARNOLD BY ww w A T TORNEVS United States Patent ROPE TEN SIGNING DEVICE Carter H. Arnold, Redwood City, Calif.

Application June 9, 1955, Serial N 0. 514,305

2 Claims. (Cl. 242-151) This invention relates to hoisting devices of the type generally employed to support scaffolds and is similar in general operation to that shown in my copending United States patent application, Serial No. 425,888, filed April 27, 1954, now Patent No. 2,742,261 issued April 17, 1956.

Heretofore, various hoisting devices have been proposed to avoid the piling up of rope on the drum carried by the scaffold which is to be raised or lowered. Such devices include one or more drums around which the rope is reeved in such a way that the friction between the rope and the drum is intended to be sufficient to prevent slippage. in this manner, the hoisting device and its associated load in effect travel along the length of rope and no piling up of the latter results at any point.

Although such prior art devices are theoretically correct, none has been adopted in practice because of various disadvantages such as unnecessary weight, lack of inherent safety in operation, impracticability in operation, complexity, and costliness.

On the other hand, this invention contemplates a hoisting device having many refinements over the prior art devices resulting in a compact, efiicient, and inherently safe hoist.

It is therefore a main object of the present invention to provide a hoisting device for scaffolds and the like which overcomes the disadvantages of prior art mechanisms of like nature.

Another object of this invention is the provision of a hoisting device incorporating novel safety features which render the same foolproof in operation.

Still another object of this invention is the provision of a hoisting device for scaffolds which includes means for preventing the formation of slack in the suspending rope at any point along the length of the latter so that the said rope is under control at all times.

Yet another object of this invention is the provision of a hoisting device adapted to be run along a length of a rope and which is more compact than those heretofore available.

It is a further object of this invention to provide a hoisting device including means for automatically tightening successive rope windings on a drum to insure adequate frictional engagement therebetween.

Other objects and advantages will become apparent from the following description taken in connection with the accompanying drawings, in which:

Fig. l is a top plan view of the hoisting device of this invention, partly broken away to show the rope windings on the drum thereof;

Fig. 2 is an elevational view of one side of the device of Fig. 1, partly broken away to show internal structure;

Fig. 3 is a sectional view taken generally along lines 3-3 of Fig. 2;

Fig. 4 is an elevational View of the other side of the device of Fig. 1;

Fig. 5 is a sectional view taken generally along line 5-5 of Fig. 4;

2,756,947 Patented July 31, 1956 Fig. 6 is an enlarged sectional view of the drive mechanism of the device of this invention; and,

Fig. 7 is a sectional view of one form of drum of the device of this invention showing representative dimensions thereof.

In detail, this invention comprises a housing which includes a pair of similar, spaced, opposed, parallel side plates 1, 2 which are secured together adjacent their upper edges by means of studs 3, 4 and adjacent their lower edges by studs 5, 6. Said studs may be reduced in the diameter at their threaded ends or provided with tubular spacers 7 (Figs. 1, 3) so that side plates 1, 2 may be positively spaced apart a predetermined distance. Although this invention will be described assuming that side plates 1, 2 are disposed vertically, it will be understood that the invention contemplates various different applications and in many instances the hoist may be used so as to dispose the side plates other than vertically.

Extending between side plates 1, 2, substantially centrally of the latter, is a shaft 8 to which is fixedly secured a drum, generally designated 9. Shaft S is rotatably mounted in bearings 10 (Fig. 3) which are preferably press fitted in side plates 1, 2. Said shaft may be held from axial movement by snap rings 11 and prevented from rotating with respect to drum 9 by a key 12.

Drum 9 is preferably provided with four peripherally extending, axially spaced grooves, although a greater or lesser number may be employed. As best seen in Fig. 7 said grooves are numbered 13, 14, 15, 16, respectively, and are preferably U-shaped or semicircular in cross section. The bottom of said grooves are undercut or recessed at 17 for the purpose of maintaining said grooves in the same shape by promoting even wear.

Grooves 1316 are adapted to receive therein the windings or turns of a rope, preferably wire rope, with the opposite ends of said rope extending away from the drum in opposite directions. Thus, referring to Fig. 2, run 18 of the rope extends upwardly from drum 9 and run 19 extends downwardly therefrom. Hereinafter, run 18 will be called the loaded run and run 19, the unloaded run. Between said runs the rope is formed with three turns, that is, one less than the number of grooves, and designated 23, 24, 25, respectively, in the drawings.

Spaced upwardly from drum 9, but relatively closely adjacent the periphery thereof are three rollers 26, 27, 23 which extend between side plates 1, 2 and are rotatably mounted at their ends therein by pressed bearings 29 (Figs. 2, 3). The peripheries or rope-engaging snrfaces of rollers 26, 27, 28 are preferably equally spaced from a center 30 which is parallel to shaft and which preferably passes through drum 9 within the periphery of the latter and closer thereto than to the center of said drum.

As best seen in Fig. 2, windings 23, 24, 25 encircle both drum 9 and rollers 26, 27, 28. Roller 27 is of a larger diameter than rollers 26, 28, and the locus of points of engagement between said rollers and said windings is preferably the arc 32 of a circle about center 3%. The effect of the above described structure is that the rope is never subjected to a sharp change in direction and at the same time an extremely compact means is provided for guiding a portion of the windings in a path spaced from the periphery of drum 9 and for leading the rope from one groove to the adjacent groove.

As best seen in Figs. 1, 3, 5, turn 23 of the rope engages more than degrees of groove 13, then joins with turn 24 in groove 14 and then turn 25 in groove 15. From groove 15 the rope runs over rollers 26, 27, 28 and enters groove 16 of drum 9 from which said rope extends diagonally over bolt 6 of the housing and downwardly into unloaded run 19. The arc of contact between the rope and drum 9 is about 240 degrees in the case of each winding; and, as is apparent, the efiiciency of the device is directly proportional to this are of con tact, which in the present case is much greater than the usual 180 degrees.

Fig. 1 shows the rope turns as they appear when drum 9 is being rotated (in a manner to be described) so that loaded. run 1% is being wound on the drum. In such a case the portions of turns 23, 24, 25 that are on the side of the drums opposite run 18 extend in the plane of the grooves from the periphery of drum 9 to roller 23. The turns then become slantingly disposed to enter the adjacent grooves on the other side of said drum. When the drum is being turned so as to wind unloaded run 19 upon the drum, the slanting portions become planar with the grooves from the drum to roller 26, and the formerly planar portions become slanted.

t is also noted that central roller 27 is provided with a pair of spaced radial flanges 31 (Figs. 1, 3, at points adjacent the outermost grooves 13, 16 on drum 9. Flanges 31 assist in guiding the rope turns from grooves on one side to adjacent grooves on the other side of said drum and to help prevent fouling of the rope turns.

The natural shifting of the rope turns, as above described, caused by changes in the tension of the rope, is not impeded in any way by rollers 26, 27, 28. However, it should be noted that the use of a grooved drum instead of the rollers shown, as has been attempted in the past, would result in the wearing and chafing of the rope which is not present in the instant device.

The provision of rollers 26, 27, 2S and their positioning as above described is an extremely important feature of the invention as said rollers provide a compact means for switching the turns of the rope. The present invention also contemplates other means for performing the functions of the rollers 26, 28.

Since the operation of the hoisting device of this invention is dependent upon friction between the rope and the grooves in drum 9, it has been found that increasing the radius from the drum center of at least one groove on the side adjacent the unloaded run 19 causes automatic tightening of the turns 23, 24, 25 on said drum. For instance, if the diameter of the drum at groove 13 is 6", and the diameter at groove 14 or is increased to 6.010", winding 24 or 25 is forced to assume such larger diameter and thereby increase the overall tension in the windings. Too great a difference in groove diameters may cause too much tension to be applied to the windings.

It has been found that, in a hoist for use with a diameter rope, a drum of 6" nominal diameter is adequate. This nominal dimension is noted by the letter A, in Fig. 7. Within manufacturing tolerances it is preferable to progressively increase the drum diameter by an increment, A, of 0.010". Hence, the diameter at groove 14 shown as A+X, at groove 15 as A-j-ZX, and at groove 16 as A+3X. Since each groove is of a semicircular cross section, as previously explained, of substantially the same diameter as the rope, this increment is approximately of the diameter of the groove cross section.

it will be noted that the differences of the grooves from the axis of drum 9 may be varied in different manners. To achieve the results of tightening the windings, it is necessary only that one of the grooves on the side of the loaded run 18 be at a lesser distance from the axis of drum 9 than one of the grooves on the side of the unloaded run 19.

To provide an additional restraint for the rope turns and to keep them at all times in engagement with the drum grooves, it is preferable to provide a tensioning device generally designated 35 (Fig. 2) for preventing slack in the rope turns. Heretofore analogous devices which have been employed but have generally comprised rollers which simultaneously engage all of the turns on the drum.

Such an arrangement has been found to promote rather than obviate the formation of slack. By the present invention only the terminal turn, adjacent unloaded run 19, is engaged. Furthermore, the use of one roller, giving only a unitary point of engagement, has in the past proved ineffectual for holding the rope in the grooves.

The tensioning device of the present invention comprises a pair of spaced rollers 36, 37 rotatably mounted between a pair of side plates 34, only one of which shows in Fig. 2. Plates 34 are generally curved with the rollers 36, 37, mounted adjacent the ends thereof and with the center swingably supported by means of a pin 38 to one end of an arm 39 which, in turn, is swingably mounted intermediate its ends on stud 5. The end of arm 39 opposite pin 38 is connected to toggle means, generally designated 40, for urging said arm in a direction to force rollers 36, 37 into engagement with the rope in groove 16 (clockwise in Fig. 2).

Toggle means 40 comprises a lever 41 pivoted as by pin 42 to said opposite end of arm 39. At a point spaced from pin 42 a pin 43 pivotally connects lever 41 to a rod 44 which is slidably mounted in an anchor pin 45, which, in turn, is rotatably mounted on side plate 2 of the housing. A compression spring 4-6, surrounding rod 44-, is interposed between anchor pin 45 and a shoulder 47 on lever 41 adjacent pin 43. Lever 41 is shown in Fig. 2 in dot-dash lines in its inoperative position, in which rollers 36, 37 are removed from the rope turn. Upon swinging arm 41 in the direction of arrow 43 to the solid line position shown, spring 46 exerts a force on said lever against pin 42 thereby rotating arm 39 in a clockwise direction to force rollers 36, 37 into engagement with the rope turn as described. It will be noted that the axis of pin $3 is placed slightly inwardly from a line between the axis of pins 42 and 45 so that spring 46 also retains lever 41 in the locked position within the housing.

Tensioning device 35 exerts a radially inwardly directed pressure along a substantial length of the rope because of the presence of the two rollers 36, 37. in addition, because both rollers are pivoted as the unit about the pin 38, each roller exerts the same amount of force and there are no forces exerted along the length of the rope as would cause the formation of slack.

The fact that rollers 36, 37 engage only the last turn of the rope adjacent the unloaded run, is extremely important in preventing the formation of slack and results in the rope being under some tension at all points along the turns that engage the grooves 13-16.

When the hoist is employed to support a scaffold from a vertically extending rope fixed at its upper end to the top of a building, loaded run 18 supports the load and unloaded run 19 supports only its own weight. It will be apparent, therefore, that the tension in the rope will decrease from run 18 through turns 23, 2 25 and will be relatively small at the point engaged by tensioning device 35. The latter should, of course, be on the side of the drum opposite that from which run 18 extends. It is due to the fact that the tension on the rope is slight adjacent run 19 that the tensioning device must exert a radially inwardly directed force without drag as above described. The lower run 19, of course, resists only its own weight and such weight contributes to the tightness of the rope turns on the drum. However, even when the length of run 19 is only a few inches, there is no chance for slippage.

The means for driving drum 9 includes a relatively large spur gear 50, keyed on drum shaft 3 externally of plate 2 of the housing. Gear 50 is in mesh with a pinion 51 mounted on a shaft 52 which is rotatably supported in pressed bearing 53 in side plates 1, 2.

As seen in Fig. 3, pinion 51 is mounted outboard on shaft 52 on the same side of the housing as gear 50. On the other end of said shaft, adjacent side plate 1, shaft 52 is provided with a rigid friction plate 54 which may be integral with said shaft (Fig. 6) or welded or otherwise secured thereto. Adjacent plate 54 on the side opposite side plate 1 is a clutch means generally designated 55 and comprising, in turn, a friction disc 56, a ratchet wheel 57, a friction disc 58, and a pressure nut 59. Friction discs 56, 58 and ratchet wheel 57 are rotatable on shaft 52. The outer end of said shaft is provided with threads 60 for threadedly receiving internally threaded pressure nut 59. It will be seen that rotating nut 59 with respect to shaft 52 in one direction causes said nut to jam friction disc 58, ratchet wheel 57 and friction disc 56 together against each other and friction plate 54.

Pressure nut 59 may be provided with an elongated handle 61 for hand operation of the hoist or may be gear connected to a motor or the like in the event power operation of the hoist is desirable. Rotation of nut 59 in an opposite direction, to cause said nut to back off from side plate 1, allows friction plates 56, 58, ratchet wheel 57 and friction disc 54 to separate and become freely rotatable one with respect to the other. A lug 62 is provided protruding axially from nut 59 into the path of a pin 63 projecting radially from shaft 52 (Fig. 1) for preventing travel of nut 59 off the end of shaft 2.

In Figs. 1, 2, it will be noted that a ratchet dog 64, rotatably mounted on a shaft 65 extending from the housing, extends into engagement with the teeth in ratchet wheel 57. Dog 64 is yieldably urged into such engaging position by a torsion spring 66 for preventing rotation of said ratchet wheel in the direction indicated by arrow 67 in Fig. 2. The direction of arrow 67 is that taken by shaft 52 upon rotation of drum 9 to unwind loaded run 18 therefrom or in moving the hoist down the rope.

Threads 60 are formed such that, when handle 61 is moved in a clockwise direction in Fig. 2 to wind loaded run 18 onto drum 9, nut 59 travels inwardly to press friction plates 56, 58, ratchet wheel 57 and friction plate 54 into a single revolvable unit. Hence, the rotation of handle 61 will be transmitted to drum 9 through friction plate 54, shaft 52, pinion 51, and spur gear 50. Ratchet wheel 57 will move in a direction opposite arrow 67 merely resting against or clicking by dog 64.

Once the load of the hoist and attached scaffold is placed on run 18, and the clockwise movement of handle 61 is ceased, drum 9 and therefore shaft 52 will be urged in a reverse direction by the tension in run 18. Handle 61 will rest in a vertical position because of its own weight. This reverse movement of shaft 52 also jams pressure nut 59 into mutual frictional engagement with friction discs 56, 58, ratchet 57 and friction plate 54. Since ratchet wheel 57 is prevented from moving in this reverse direction (arrow 67) by dog 64, the hoist cannot fall.

Movement of handle 61 in a counterclockwise direction, however, decreases the frictional pressure between the friction discs, the ratchet wheel and friction plate 54 to an extent sufiicient to allow shaft 52 to slip with respect to said ratchet wheel. This slippage of shaft 52 is at all times controlled by the movement of pressure nut 59 by handle 61, and therefore the downward movement of the hoist on the rope is adjusted as desired by the operator. If, at any time, counterclockwise movement of handle 61 is stopped, shaft 52 immediately catches up thereby jamming friction disc 56 between friction plate 54 and ratchet wheel 57 to prevent further downward movement of the hoist.

It is obvious that other means could be used to urge nut 59 and the associated parts of the clutch 55 into mutual frictional engagement such as a face cam secured on shaft 52 and engageable with a mating cam on nut 59. The clutch device shown in Fig. 5, however, has been found to be more practical.

Rigidly mounted on stud 3 adjacent side plate 2 is a grooved guide or fairlead 69 (Figs. 1, 2, 4) having its grooved edge in line with loaded run 18 extending from drum 9. In effect, groove 70 completes the projected 6 half circle of groove 13 on said drum. Fairlead '69 therefore acts to guide run 18 into groove 13.

As a valuable safety feature the present invention includes an elongated clamping arm generally designated 71 (Figs. 1, 2, 4), which cooperates with guide 69 in a manner now to be described. Arm 71 may be formed from a heavy plate and is swingably supported intermediate its ends on a stud 72 extending between and secured to side plates 1, 2. Arm 71 is coplanar with fairlead 69 and is formed with an arcuate, grooved end 73 to receive the side of loaded run 18 that is opposite the side engaged by fairlead 69.

End 73 of arm 71 is formed to the arc of a circle having a center opposite stud 72 from end 73 so that clockwise swinging of arm 71 (Fig. 2) urges the grooved end 73 to clamping relation with fairlead 69 so as to clamp the rope run 18 therebetween (Figs. 1, 4). The end 74 of arm 71 that is opposite the clamping end is relatively long and of sufiicient mass to urge the arm into clamping engagement of upper run 18 of the rope at all times due to gravity.

Thus, if it is assumed that run 18 is hanging stationary and vertical and a load is applied to the housing so as to rotate from 9 clockwise (Fig. 2) the housing will tend to move downwardly relative to run 18 and securely clamp the rope against fairlead 69, thereby positively preventing such downward movement. However, if it is assumed that drum 9 is positively rotated so as to wind the run 18 therein, the housing moves up relative to stationary run 18 and swings arm 76 counterclockwise away from clamping position (Fig. 2). It will be understood that arm 71 is always in engagement with run 18 but has no effect thereon except when the housing tends to fall relative thereto. When it is desired to move the housing downward relative to run 18, it is merely necessary for the operator to lift the end 74 of arm 71 out of clamping engagement with run 18. This may be facilitated by running the device upwardly slightly.

With respect to Fig. 2, it is obvious that a spring may be employed to urge arm 71 in a clockwise direction into clamping engagement with loaded rope run 18. The arm illustrated has suflicient unbalanced weight in the portion 74 to effect a proper automatic working of the safety device when used with a vertically extending rope. However, additional yieldable urging on the arm may be desirable in many instances, especially when the device is employed with a rope inclined to the vertical or the horizontal. As previously mentioned, the novel combination of clamping arm 71 and fairlead 69 also functions to guide run 18 into the groove 13 on drum 9 at all times, and there is no chance of the rope separating from fairlead 69.

Inasmuch as relative slippage between the rope and the drum 9 is always impossible because of the frictional engagement of the rope within the drum grooves, it is merely necessary to prevent the accidental rotation of drum 9, if an additional safety device is desired. To this end a pawl 75 (Fig. 4) may be swingably mounted on the end of shaft 65 opposite dog 64 and outboard of side plate 2 (Fig. 5). Said pawl is unbalanced so as to be urged into engagement with the teeth of gear 50 (Fig. 4) by gravity. It is obvious that a spring could be used to yieldably urge pawl 75 into engagement with gear 50 if required. Pawl 75 is shaped so as to prevent counterclockwise rotation of gear 50 (Fig. 4) which is equivalent to downward movement of the housing with respect to the rope.

In order that pawl 75 will be disengaged from gear 50 only upon unclamping of the brake arm 71, pawl 75 is provided with a pin 76 eccentric with respect to shaft 65 and extending axially thereof through an opening 77 in side plate 2 into the path of end 73 of clamping arm 71. Hence, upon rotation of arm 71 in a clockwise direction (Fig. 4) to unclamp run 18 of the rope, end 73 strikes pin 76 to rotate pawl 75 out of engagement 7 with gear 50. This allows downwardly movement of the hoist with respect to run 18 of the rope in the manner previously described.

Although the present invention has many applications, its greatest use lies in supporting scaffold or the like from a pair of stirrups or hangers 78 (Fig. 4) at opposite ends thereof, in which case a hoisting device is employed with each such stirrup. Ordinarily, such stirrups are formed from steel rod or strap and are provided with an eye portion '79 from which the scaffold is suspended. In such a case side plates 1, 2 are preferably provided with an offset portion so that stud 5 is in vertical alignment with loaded run 18 of the rope.

In order to position the eye portion 79 in vertical alignment with the run 18, the former may be directly carried by stud 5 in Fig. 4. A positioning collar on stud 5 may serve to hold the vertical alignment between run 18 and the eye 79 of the stirrup. By the above described structure the line of action is always vertical and the housing is therefore held vertical at all times.

When used with a 650 pound working load, it has been found that side plates 1, 2 need not be longer than 12", thus making an extremely compact, lightweight unit which is easily handled by one man without assistance.

In use, the rope is easily reeved around drum 9 and rollers 26, 27, 28 to set up the hoist because the tensioning device 35 may be swung outwardly by means of the lever 41.

The safety features above described, including the features of clutch 55, make the hoist acceptable under the most stringent state laws. There is no opportunity for sudden jerks in the scaffold taking place as in the case when the rope is wound unevenly on a drum as in conventional hoists.

An extremely important feature of the invention is that the load bearing stirrup and the loaded run of the wire rope are in perfect vertical alignment as seen in Fig. 4. This constitutes an extremely beneficial safety feature inasmuch as there is no tendency for the hoisting device to tilt from an upright position when the load is applied or removed.

Although the invention has been described and illustrated in detail, such is not to be taken as restrictive thereof, since it is obvious that modifications could be made therein without departing from the spirit and scope of the invention.

I claim:

1. A tensioning device for applying lateral pressure to a moving rope or the like comprising: a pair of rollers rotatably mounted on a common mount, an arm swing ably mounted intermediate its ends to a support, and pivotally connected at one of its ends to said mount, a toggle mechanism operatively connected to the end of said arm opposite said one end, and a spring for urging said toggle mechanism and said arm in a direction for applying lateral pressure through said rollers to said rope.

2. A tensioning device for applying lateral pressure to a moving rope or the like comprising: a pair of rollers rotatably mounted on a common mount, an arm swingably mounted intermediate its ends to a support, and pivotally connected at one of its ends to said mount, a toggle mechanism operatively connected to the end of said arm opposite said one end, said mechanism including a lever swingably connected at one end to said opposite end of said arm and a link swingably connected to said lever intermediate the ends of the latter, a member rotatable relative to said support and slidably connected to said link, a spring interposed between said member and said lever for urging the latter and said arm in a direction for applying lateral pressure through said rollers to said rope.

References Cited in the file of this patent UNITED STATES PATENTS 606,424 Lamb June 28, 1898 1,438,674 Trumm Dec. 12, 1922 1,555,544 Anthony Sept. 29, 1925 1,610,850 Davidson Dec. 14, 1926 1,682,083 Johnston Aug. 28, 1928 2,453,581 Moore Nov. 9, 1948 2,561,139 Sasgen July 17, 1951 2,662,732 Allenbaugh Dec. 15, 1953 2,662,733 Allenbaugh Dec. 15, 1953 FOREIGN PATENTS 566,435 Germany Dec. 16, 1932 

